1. Field of the Invention
This invention relates to the localization of excessive temperature conditions.
2. Description of the Prior Art
It is sometimes desirable -- if not necessary -- to indicate the occurrence of an excessive temperature along a continuous path such as through a building or through a conduit carrying telephone cables. U.S. Pat. No. 2,972,132, issued to C. B. Putney on Feb. 14, 1961, for example, discloses apparatus for producing such indications. The Putney apparatus comprises a continuous thermoplastic tubing strung along the path being supervised. The tubing is filled with a gas under pressure and connected to a switch responsive to a loss in the tubing pressure. The tubing and the pressure are selected so that the tubing ruptures when the temperature adjacent to the tubing reaches a predetermined excessive level. When a rupture occurs, the gas within the tubing is released and the pressure sensitive switch responds to give an alarm.
The above-mentioned Putney apparatus is adequate for indicating the occurrence of excessive temperature. However, it is inadequate when one also wishes to know the approximate location of the excessive temperature. In the case of telephone cables in conduits, for example, it is highly desirable to know the approximate location of any overheating. In particular, not only would time be saved in finding the problem but it is possible that corrective action can be instituted before the telephone cables are damaged to the extent that they must be replaced.